The invention relates to a process and an arrangement for exchanging spools and packages at an individual spinning unit of a spinning machine having a plurality of spinning units of this type which each produce at least one yarn which is withdrawn by means of a withdrawal device and is wound onto a spool package by means of a winding device which contains a cross-winding yarn guide distributing the yarn in longitudinal direction of the spool package, in which case, after a given filling ratio of the spool package is reached, the further yarn production at the respective spinning unit is interrupted and a yarn end is wound onto the spool package.
In certain spinning processes, particularly in ring spinning, it is customary that, at the end of a package build-up, i.e., before the package is exchanged for a spool, a yarn reserve is deposited at a certain point on the spinning package, such as an underwinding or an overwinding. As a result, it is achieved that the yarn guides (ring rail with traveller) are controlled correspondingly. In this case, it is a prerequisite that all spinning points terminate their package build-up at the same time, i.e., have reached the desired filling ratio at the same time. However, this is not the case in other spinning machines, for example, in the case of open-end rotor spinning or open-end air spinning and particularly also in the spinning process (DE-A 36 34 464) in which only two prestrengthened yarn components are spun which subsequently are wound onto a spool package as a double yarn. This package is used as a feeding package for a twisting operation. It frequently happens in this process that the spool packages, at the individual spinning points, have reached the given filling ratio at very different times. The spinning operation at these individual spinning units is then interrupted. In this case, the yarn end of the yarn moving through a cross-winding yarn guide is wound onto the spool package and will then be located at a not predetermined point somewhere on the circumference of the spool package. Frequently, there are problems in this case with respect to finding and withdrawing the yarn end, particularly for automatic devices which have the purpose of carrying out this work. These problems are particularly severe in the process in which the two only prestrengthened yarn components are wound onto a spool package as a double yarn. There is the added risk, in this case, that, on the one hand, the ends of the two yarn components are deposited at different points on the spool package so that they cannot be found simultaneously and therefore the double yarn cannot be withdrawn correctly. On the other hand, the strength of the two yarn components wound up as a double yarn is relatively low so that a yarn searching nozzle of an automatic device must not affect the surface of the spool package by means of a high pressure. Otherwise, there is the risk that the upper layers of the double yarn are damaged.
In the case of a spooling frame, it is also known (DE-A 17 60 243), when the given filling ratio of the spool package is reached, to lift the yarn at an unreduced speed out of the cross-winding yarn guide by means of a lever which can be brought into the moving path of the yarn and to deflect the yarn such that the final windings are deposited in parallel to a predetermined point.
An object of the invention is to provide a process and an arrangement of the initially mentioned type in which the refinding of a yarn end on the full package is facilitated particularly for automatic devices.
This object is achieved in that, when a given filling ratio is reached, the yarn which continues to move to the spool package is disengaged from the cross-winding yarn guide and subsequently, as final windings, is wound on an area delimited in longitudinal direction of the spool package, onto the spool package.
As a development of preferred embodiments of the invention, it is provided that when a given filling ratio is reached, the winding speed of the spool package is reduced.
By reducing the winding speed of the spool package, which particularly also includes a stopping of the spool package, the yarn tension is loosened to such an extent that the yarn can be lifted out of the cross-winding yarn guide without any difficulty. It may then be wound onto the spool package at a defined point without the occurrence of inadmissible loads. The finding of this yarn end will then be facilitated greatly for an automatic device. For this purpose, a suction nozzle is used, as a rule, which, corresponding to the possible depositing area, needs to be only relatively narrow. Since the yarn end can also be found within a relatively short time, the surface of the spool package is exposed to the suction effect only during a relatively short period of time.
In a further development of the invention, it is provided that the spool package is first separated from the winding device and then the yarn is disengaged from the cross-winding yarn guide, in which case the yarn which continues to be produced for a given time period is stored in a storage device connected behind the withdrawal device subsequently the yarn is wound up as final windings while the spool package is driven again while bypassing the cross-winding yarn guide. This results in the advantage that the spool package may have come to a standstill before the yarn is disengaged from the cross-winding yarn guide. The yarn which is then still contained in the storage device may then, at a later point in time, at an appropriate and particularly a reduced winding speed, be wound onto the spool package so that the yarn is not stressed unacceptably.
In a further development of the invention, it is provided that the yarn leaving the storage device is cut off in front of the end created by the interruption of the spinning operation. As a result, it is avoided that the usually thinned-out yarn end, which was created when the spinning unit was switched off, is wound onto the spool package.
In a further development of the invention, it is provided that the yarn end wound up during the formation of the final windings, particularly when a double yarn is produced from prestrengthened yarn components, is strengthened before moving onto the spool package. In this case, it is expedient for the ends of the two yarn components of a double yarn to be connected with one another before moving onto the spool package. As a result, it is achieved that the ends of the double yarn are definitely situated at the same point on the spool package and are also picked up simultaneously. In particular, in the case of a double yarn consisting of prestrengthened yarn components, it is expedient for the connecting of the two yarn components to take place along a certain length, for example, along a length of 0.5 meters. As a result, a yarn piece is available during the subsequent further processing which has a higher strength and can therefore be handled more easily and with a reduced risk of a yarn breakage. This prestrengthening and/or connecting with one another is also advantageous when the final windings are not deposited at a certain given point but are situated at a random point on the surface of the spool package determined by the cross-winding yarn guide.
In a further development of the invention, it is provided in an arrangement that devices for detecting the filling ratio of the spool package are connected to devices for reducing the winding speed and to devices for lifting the yarn out of the cross-winding yarn guide. In a first embodiment, it is provided that each spinning unit is equipped with devices for lifting the spool package off the winding device. In addition, it is provided in this case that each spinning unit is equipped with a yarn guiding device which can be brought into the moving path in front of the spool package. In addition it is provided in this embodiment in an expedient development that each spinning unit is equipped with a device for storing the spun yarn which is arranged behind the withdrawal device in the travel direction of the yarn. In order to obtain a reinforced end in this embodiment, each spinning unit is equipped with a device for the prestrengthening of the yarn which is preferably arranged in the travel direction of the yarn behind the device for the storing. It is also expedient for a cutting device to be provided which is connected behind the device for the storing in the travel direction of the yarn.
In another development of the invention, it is provided that a device for reducing the winding speed and/or devices for lifting the yarn out of the cross-winding yarn guide and/or a device for storing the yarn and/or a device for interrupting the spinning operation and/or a device for strengthening the yarn and/or a cutting device and/or an auxiliary winding device for the spool package are housed in a drivable servicing device which, as required, can be applied to one of the spinning units respectively. This servicing device can not only carry out the preparing of a spool package achieving the desired filling ratio but also the complete exchange of the spool and the package.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.